Phosphorus needs to gain three electrons to achieve a stable electron configuration.
Sulfur needs to gain 2 electrons to have the electon configuration of Argon
They should gain 2 electrons to attain noble gas electronic configuration. (it doesn't become a noble gas as the number of protons are not same)
Selenium needs to gain two electrons to achieve a stable electron configuration. By gaining two electrons, selenium will have a complete outer energy level (valence shell), which is the most stable configuration for an atom.
Barium loses 2 as it is in group 2 and it's easier to lose two than to gain more than this.
Oxygen needs to gain 2 electrons to reach an octet, as it has 6 valence electrons in its outer shell and requires a total of 8 electrons to have a stable octet configuration.
Phosphorus has to gain a total of 3 electrons to achieve a noble gas configuration. You can find this for any non-metal because the last digit of its group number is the number of valence electrons it has. For example Phosphorus has 5 and Sulfur has 6. In order to achieve a noble gas electron configuration, you must have 8 valence electrons, so phosphorus must gain 3.
Phosphorus has 5 valence electrons and it needs 3 more electrons to complete its octet and achieve stability.
Phosphorus need 3 electrons to complete its octet.
Its outer shell needs 3 more electrons (because 2+3=5) you need 8 in order for the outer shell to become stable being that there is 5 on the outer shell already what plus 5 gives you 8 3 of course so that why you add 3.
Phosphorus should gain 3 electrons and form P3- ion to attain a noble gas configuration
In a reaction u need two valence electrons to gain or share two valence electrons.
They need to gain them.
It needs to lose, or gain, electrons.
Sulfur needs to gain 2 electrons to have the electon configuration of Argon
the pent in pentachloride refers to the chlorine in the molecule, therefore the molecular formula of the stated cemical is PCl5...although I'm not sure if this can exist because these two must form covalently (both need to gain electrons to gain full valence shell)
electrons
Oxygen should gain 2 electrons to achieve noble gas configuration